'\" et
.TH SETLOCALE "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
setlocale
\(em set program locale
.SH SYNOPSIS
.LP
.nf
#include <locale.h>
.P
char *setlocale(int \fIcategory\fP, const char *\fIlocale\fP);
.fi
.SH DESCRIPTION
The functionality described on this reference page is aligned with the
ISO\ C standard. Any conflict between the requirements described here and the
ISO\ C standard is unintentional. This volume of POSIX.1\(hy2017 defers to the ISO\ C standard.
.P
The
\fIsetlocale\fR()
function selects the appropriate piece of the global locale, as specified
by the
.IR category
and
.IR locale
arguments, and can be used to change or query the entire global locale
or portions thereof. The value LC_ALL for
.IR category
names the entire global locale; other values for
.IR category
name only a part of the global locale:
.IP LC_COLLATE 12
Affects the behavior of regular expressions and the collation
functions.
.IP LC_CTYPE 12
Affects the behavior of regular expressions, character classification,
character conversion functions, and wide-character functions.
.IP LC_MESSAGES 12
Affects the affirmative and negative response expressions returned by
\fInl_langinfo\fR()
and the way message catalogs are located. It may also affect the
behavior of functions that return or write message strings.
.IP LC_MONETARY 12
Affects the behavior of functions that handle monetary values.
.IP LC_NUMERIC 12
Affects the behavior of functions that handle numeric values.
.IP LC_TIME 12
Affects the behavior of the time conversion functions.
.P
The
.IR locale
argument is a pointer to a character string containing the required
setting of
.IR category .
The contents of this string are implementation-defined. In addition,
the following preset values of
.IR locale
are defined for all settings of
.IR category :
.IP "\&\(dqPOSIX\(dq" 12
Specifies the minimal environment for C-language translation called the
POSIX locale. The POSIX locale is the default global locale at entry to
\fImain\fR().
.IP "\&\(dqC\(dq" 12
Equivalent to
.BR \(dqPOSIX\(dq .
.IP "\&\(dq\|\(dq" 12
Specifies an implementation-defined native environment.
The determination of the name of the new locale for the specified
category depends on the value of the associated environment
variables,
.IR LC_*
and
.IR LANG ;
see the Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 7" ", " "Locale"
and
.IR "Chapter 8" ", " "Environment Variables".
.IP "A\ null\ pointer" 12
Directs
\fIsetlocale\fR()
to query the current global locale setting and return the name
of the locale if
.IR category
is not LC_ALL, or a string which encodes the locale name(s) for all of
the individual categories if
.IR category
is LC_ALL.
.P
Setting all of the categories of the global locale is similar to
successively setting each individual category of the global locale, except
that all error checking is done before any actions are performed. To
set all the categories of the global locale,
\fIsetlocale\fR()
can be invoked as:
.sp
.RS 4
.nf

setlocale(LC_ALL, "");
.fi
.P
.RE
.P
In this case,
\fIsetlocale\fR()
shall first verify that the values of all the environment variables it
needs according to the precedence rules (described in the Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 8" ", " "Environment Variables")
indicate supported locales. If the value of any of these environment
variable searches yields a locale that is not supported (and non-null),
\fIsetlocale\fR()
shall return a null pointer and the global locale shall not be changed. If
all environment variables name supported locales,
\fIsetlocale\fR()
shall proceed as if it had been called for each category, using the
appropriate value from the associated environment variable or from the
implementation-defined default if there is no such value.
.P
The global locale established using
\fIsetlocale\fR()
shall only be used in threads for which no current locale has been
set using
\fIuselocale\fR()
or whose current locale has been set to the global locale using
.IR uselocale (LC_GLOBAL_LOCALE) .
.P
The implementation shall behave as if no function defined in this volume of POSIX.1\(hy2017 calls
\fIsetlocale\fR().
.P
The
\fIsetlocale\fR()
function need not be thread-safe.
.SH "RETURN VALUE"
Upon successful completion,
\fIsetlocale\fR()
shall return the string associated with the specified category for the
new locale. Otherwise,
\fIsetlocale\fR()
shall return a null pointer and the global locale shall not be changed.
.P
A null pointer for
.IR locale
shall cause
\fIsetlocale\fR()
to return a pointer to the string associated with the specified
.IR category
for the current global locale. The global locale shall not be changed.
.P
The string returned by
\fIsetlocale\fR()
is such that a subsequent call with that string and its associated
.IR category
shall restore that part of the global locale. The application shall
not modify the string returned.
The returned string pointer might be invalidated or
the string content might be overwritten by a subsequent call to
\fIsetlocale\fR().
The returned pointer might also be invalidated if the calling
thread is terminated.
.SH ERRORS
No errors are defined.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
The following code illustrates how a program can initialize the
international environment for one language, while selectively modifying
the global locale such that regular expressions and string operations
can be applied to text recorded in a different language:
.sp
.RS 4
.nf

setlocale(LC_ALL, "De");
setlocale(LC_COLLATE, "Fr@dict");
.fi
.P
.RE
.P
Internationalized programs can initiate language operation according
to environment variable settings (see the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 8.2" ", " "Internationalization Variables")
by calling
\fIsetlocale\fR()
as follows:
.sp
.RS 4
.nf

setlocale(LC_ALL, "");
.fi
.P
.RE
.P
Changing the setting of
.IR LC_MESSAGES
has no effect on catalogs that have already been opened by calls to
\fIcatopen\fR().
.P
In order to make use of different locale settings while multiple
threads are running, applications should use
\fIuselocale\fR()
in preference to
\fIsetlocale\fR().
.SH RATIONALE
References to the international environment or locale in the following
text relate to the global locale for the process. This can be overridden
for individual threads using
\fIuselocale\fR().
.P
The ISO\ C standard
defines a collection of functions to support internationalization.
One of the most significant aspects of these functions is a facility
to set and query the \fIinternational environment\fP.
The international environment is a repository of information that
affects the behavior of certain functionality, namely:
.IP " 1." 4
Character handling
.IP " 2." 4
Collating
.IP " 3." 4
Date/time formatting
.IP " 4." 4
Numeric editing
.IP " 5." 4
Monetary formatting
.IP " 6." 4
Messaging
.P
The
\fIsetlocale\fR()
function provides the application developer with the ability to set all
or portions, called \fIcategories\fP, of the international environment.
These categories correspond to the areas of functionality mentioned
above. The syntax for
\fIsetlocale\fR()
is as follows:
.sp
.RS 4
.nf

char *setlocale(int \fIcategory\fP, const char *\fIlocale\fP);
.fi
.P
.RE
.P
where
.IR category
is the name of one of following categories, namely:
.sp
.RS
LC_COLLATE
LC_CTYPE
LC_MESSAGES
LC_MONETARY
LC_NUMERIC
LC_TIME
.RE
.P
In addition, a special value called LC_ALL
directs
\fIsetlocale\fR()
to set all categories.
.P
There are two primary uses of
\fIsetlocale\fR():
.IP " 1." 4
Querying the international environment to find out what it is set to
.IP " 2." 4
Setting the international environment, or
.IR locale ,
to a specific value
.P
The behavior of
\fIsetlocale\fR()
in these two areas is described below. Since it is difficult to
describe the behavior in words, examples are used to illustrate the
behavior of specific uses.
.P
To query the international environment,
\fIsetlocale\fR()
is invoked with a specific category and the null pointer as the
locale. The null pointer is a special directive to
\fIsetlocale\fR()
that tells it to query rather than set the international environment.
The following syntax is used to query the name of the international
environment:
.sp
.RS 4
.nf

setlocale({LC_ALL, LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, \e
    LC_NUMERIC, LC_TIME},(char *) NULL);
.fi
.P
.RE
.P
The
\fIsetlocale\fR()
function shall return the string corresponding to the current
international environment. This value may be used by a subsequent call to
\fIsetlocale\fR()
to reset the international environment to this value. However, it
should be noted that the return value from
\fIsetlocale\fR()
may be a pointer to a static area within the function and is not
guaranteed to remain unchanged (that is, it may be modified by a
subsequent call to
\fIsetlocale\fR()).
Therefore, if the purpose of calling
\fIsetlocale\fR()
is to save the value of the current international environment so it can
be changed and reset later, the return value should be copied to an
array of
.BR char
in the calling program.
.P
There are three ways to set the international environment with
\fIsetlocale\fR():
.IP "\fIsetlocale\fP(\fIcategory\fP,\ \fIstring\fP)" 6
.br
This usage sets a specific
.IR category
in the international environment to a specific value corresponding to
the value of the
.IR string .
A specific example is provided below:
.RS 6 
.sp
.RS 4
.nf

setlocale(LC_ALL, "fr_FR.ISO-8859-1");
.fi
.P
.RE
.P
In this example, all categories of the international environment are
set to the locale corresponding to the string
.BR \(dqfr_FR.ISO-8859-1\(dq ,
or to the French language as spoken in France using the ISO/IEC\ 8859\(hy1:\|1998 standard codeset.
.P
If the string does not correspond to a valid locale,
\fIsetlocale\fR()
shall return a null pointer and the international environment is not
changed. Otherwise,
\fIsetlocale\fR()
shall return the name of the locale just set.
.RE
.IP "\&\fIsetlocale\fP(\fIcategory\fP,\ \(dqC\(dq)" 6
.br
The ISO\ C standard states that one locale must exist on all conforming
implementations. The name of the locale is C and corresponds to a
minimal international environment needed to support the C programming
language.
.IP "\&\fIsetlocale\fP(\fIcategory\fP,\ \(dq\^\(dq)" 6
.br
This sets a specific category to an implementation-defined default.
This corresponds to the value of the environment variables.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.ad l
.IR "\fIcatopen\fR\^(\|)",
.IR "\fIexec\fR\^",
.IR "\fIfprintf\fR\^(\|)",
.IR "\fIfscanf\fR\^(\|)",
.IR "\fIisalnum\fR\^(\|)",
.IR "\fIisalpha\fR\^(\|)",
.IR "\fIisblank\fR\^(\|)",
.IR "\fIiscntrl\fR\^(\|)",
.IR "\fIisdigit\fR\^(\|)",
.IR "\fIisgraph\fR\^(\|)",
.IR "\fIislower\fR\^(\|)",
.IR "\fIisprint\fR\^(\|)",
.IR "\fIispunct\fR\^(\|)",
.IR "\fIisspace\fR\^(\|)",
.IR "\fIisupper\fR\^(\|)",
.IR "\fIiswalnum\fR\^(\|)",
.IR "\fIiswalpha\fR\^(\|)",
.IR "\fIiswblank\fR\^(\|)",
.IR "\fIiswcntrl\fR\^(\|)",
.IR "\fIiswctype\fR\^(\|)",
.IR "\fIiswdigit\fR\^(\|)",
.IR "\fIiswgraph\fR\^(\|)",
.IR "\fIiswlower\fR\^(\|)",
.IR "\fIiswprint\fR\^(\|)",
.IR "\fIiswpunct\fR\^(\|)",
.IR "\fIiswspace\fR\^(\|)",
.IR "\fIiswupper\fR\^(\|)",
.IR "\fIiswxdigit\fR\^(\|)",
.IR "\fIisxdigit\fR\^(\|)",
.IR "\fIlocaleconv\fR\^(\|)",
.IR "\fImblen\fR\^(\|)",
.IR "\fImbstowcs\fR\^(\|)",
.IR "\fImbtowc\fR\^(\|)",
.IR "\fInewlocale\fR\^(\|)",
.IR "\fInl_langinfo\fR\^(\|)",
.IR "\fIperror\fR\^(\|)",
.IR "\fIpsiginfo\fR\^(\|)",
.IR "\fIstrcoll\fR\^(\|)",
.IR "\fIstrerror\fR\^(\|)",
.IR "\fIstrfmon\fR\^(\|)",
.IR "\fIstrsignal\fR\^(\|)",
.IR "\fIstrtod\fR\^(\|)",
.IR "\fIstrxfrm\fR\^(\|)",
.IR "\fItolower\fR\^(\|)",
.IR "\fItoupper\fR\^(\|)",
.IR "\fItowlower\fR\^(\|)",
.IR "\fItowupper\fR\^(\|)",
.IR "\fIuselocale\fR\^(\|)",
.IR "\fIwcscoll\fR\^(\|)",
.IR "\fIwcstod\fR\^(\|)",
.IR "\fIwcstombs\fR\^(\|)",
.IR "\fIwcsxfrm\fR\^(\|)",
.IR "\fIwctomb\fR\^(\|)"
.ad b
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 7" ", " "Locale",
.IR "Chapter 8" ", " "Environment Variables",
.IR "\fB<langinfo.h>\fP",
.IR "\fB<locale.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
